1. Field of the Invention
The present invention relates to a balanced splitter, in particular, a balanced splitter for use in mobile communication devices, or the like.
2. Description of the Related Art
With the trend toward higher signal frequency, an increasing number of communication devices use a balanced signal for the purpose of improved anti-noise characteristics, and the like. For this reason, there is a need for an unbalanced/balanced converter for converting an unbalanced signal into a balanced signal. Further, there is also a need for a splitter for splitting a signal into two signals depending on the intended applications. Accordingly, there is a growing need for a component combining the functions of both the converter and the splitter, that is, an “unbalanced output/balanced input splitter (balanced splitter)” for splitting a single unbalanced signal into two balanced signals.
As shown in FIG. 13, an unbalanced output/balanced input splitter (balanced splitter) 1 is obtained by combining one unbalanced output/unbalanced input splitter (a generally known splitter) 2 that splits an unbalanced signal input from an unbalanced terminal 5 into two signals, and two unbalanced/balanced converters (so-called baluns) 3, 4 that convert each of the two split unbalanced signals into a balanced signal. The balanced signals exiting the unbalanced/balanced converters 3, 4 are output from first balanced terminals 6a, 6b and second balanced terminals 7a, 7b, respectively.
Alternatively, the unbalanced output/balanced input splitter (balanced splitter) is obtained by combining one unbalanced/balanced converter (so-called balun), which converts an unbalanced signal into a balanced signal, with one balanced input/balanced output splitter that splits the one balanced signal output from the unbalanced/balanced converter into two signals.
Known unbalanced/balanced converters include those described in JP 2001-94316 A and JP 2001-168607 A. Based on JP 2001-94316 A and JP 2001-168607 A, the unbalanced output/balanced input splitter (balanced splitter) 1 shown in the block circuit diagram of FIG. 13 is illustrated in more detail in the electric circuit diagram of FIG. 14. The balanced splitter 1 is composed of ten ¼ wavelength strip lines 11 to 20 and one resistor R.
However, when the balanced splitter 1 is constructed by combining the splitter 2 and the baluns 3, 4, each of which are separate components, a problem arises in that the number of components increases. Further, as shown in FIG. 14, when the separate components 2 to 4 are simply integrated into one component, the internal circuit configuration of the component becomes rather complex leading to such problems as high manufacturing cost and large insertion loss.